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The bignose shark (''Carcharhinus altimus'') is a species of requiem shark, in the family Carcharhinidae. Distributed worldwide in tropical and subtropical waters, this migratory shark frequents deep waters around the edges of the continental shelf. It is typically found at depths of , though at night it may move towards the surface or into shallower water. The bignose shark is plain-colored and grows to at least in length. It has a long, broad snout with prominent nasal skin flaps, and tall, triangular upper teeth. Its pectoral fins are long and almost straight, and there is a ridge on its back between the two dorsal fins. Hunting close to the sea floor, the bignose shark feeds on bony and cartilaginous fishes, and cephalopods. It is viviparous, meaning the embryos are sustained to term via a placental connection. Females bear litters of three to15 pups after a 10-month gestation period. Despite its size, this shark lives too deep to pose much danger to humans. It is caught incidentally by commercial fisheries in many parts of its range; the meat, fins, skin, liver oil, and offal may be used. The International Union for Conservation of Nature presently lacks enough information to assess the global conservation status of this species. However, the various fishing pressures within its range are cause for concern given its slow reproductive rate, and it may have already declined in the northwestern Atlantic and elsewhere. ==Taxonomy and phylogeny== Shark expert Stewart Springer described the bignose shark as ''Eulamia altima'' in a 1950 issue of the scientific journal ''American Museum Novitates''. Later authors have regarded the genus ''Eulamia'' as a synonym of ''Carcharhinus''. The specific epithet ''altimus'' is derived from the Latin ''altus'' ("deep"), and refers to the shark's deepwater habits. The type specimen is an immature female long, caught off Cosgrove Reef in the Florida Keys on April 2, 1947. An alternate common name for this species is Knopp's shark, originally used by Florida fishery workers since before the species was described.〔〔 }} }} }} }} Phylogenetic studies published by Jack Garrick in 1982 and Leonard Compagno in 1988, based on morphology, placed the bignose shark in the "''obscurus'' group" of ''Carcharhinus'', centered on the dusky shark (''C. obscurus'') and the Galapagos shark (''C. galapagensis''). The group consists of large, triangular-toothed sharks with a ridge between the dorsal fins.〔〔 Gavin Naylor's 1992 study, based on allozyme sequences, upheld and further resolved this "ridge-backed" group. The bignose shark was found to be the sister species of the sandbar shark (''C. plumbeus''), with the two forming one of the group's two branches.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「bignose shark」の詳細全文を読む スポンサード リンク
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